Orthoses are mechanical devices which impose forces upon a limb of a patient and which can be used for a variety of different purposes. For example, orthoses can be provided for supportive, functional, corrective or protective purposes, or indeed for a combination of these.
Ankle-foot orthoses are typically used to provide protection to the ankle and foot of a patient as well as to provide support against excessive plantarflexion, or “foot-drop” as it is more colloquially known Foot plantarflexion is a medical condition that results from disease, trauma or congenital abnormality. Patients affected by the condition typically experience difficulty in walking as their feet tend to drop when lifted off the ground, and to avoid stumbling they typically have to lift their foot higher than they would otherwise have to. It is also not atypical for patients to have problems during the swing through phase of their gait cycle, as a typical sufferer will tend also to exhibit poor, or impaired, dorsiflexion.
The primary function of an ankle-foot orthosis to provide a resistance to plantarflexion which helps keep the patient's foot in the correct position when the foot is lifted off the ground. As well as this resistive function, a good ankle-foot orthosis should also provide a degree of assistance to dorsiflexion during the swing through phase of the patient's gait.
A variety of different ankle-foot orthoses have previously been proposed for resisting plantarflexion, and in some cases for additionally assisting dorsiflexion.
FIGS. 1 and 2 are schematic representations of what is commonly known in the art as an “under foot” orthosis 10. As this colloquial name suggests, the orthosis fits under the foot, and in this case outside of a shoe 12. This particular device cannot be worn without a shoe, and as such the shoe is an integral component of the orthosis. The orthosis comprises a pair of supporting metal rods 14, one connected to either side of the shoe 12 in the region of the heel 16. The rods are each connected to the shoe by means of a plantarflexion stop 18 that resists foot drop, and springs (not shown) may be provided to assist dorsiflexion. The upper ends of the rods are connected to a supporting band which is adapted to be secured about the calf of a patient. From FIG. 2 it can be seen that the supporting strap functions to secure the orthosis about the patient's calf, and the plantarflexion stops 18 and shoe 12 provide support under the patient's foot to resist plantarflexion.
FIGS. 3 and 4 illustrate another previously proposed “under foot” orthosis which must also be used with a shoe that provides close contact between the shoe and the foot in the region of the instep. In this example, the orthosis 22 comprises a one-piece plastics moulding 24 which comprises a calf-abutting region 26 and a sole abutting region 28. The top of the calf-abutting region 26 is provided with a closure mechanism 27 that enables the device to be secured to the calf of a patient. The sole abutting region 28 acts in conjunction with the shoe 30 to support the foot of the patient. The stiffness of the plastics moulding and the shape thereof in the region of the ankle defines the amount of resistance to plantarflexion. If more resistance is required, then the gap across the front of the ankle can be reduced, or the stiffiess of the plastics material can be increased.
FIG. 5 is a functional equivalent to the orthosis of FIGS. 3 and 4, and as such is similar in many respects to the orthosis shown in FIGS. 3 and 4. The chief difference is that the device shown in FIG. 5 is an “over foot” orthosis, meaning that the orthosis fits over the front (dorsal) aspect of the foot, rather than under it as in the device of FIGS. 1 to 4. As shown the device comprises a plastics shell 32 which is worn up against the shin, and which is secured around the calf by means of an appropriate securing band 34. The orthosis includes a stirrup 36 which fits over the foot in the region of the instep, and it is the stirrup which provides the patient with a resistance to plantarflexion.
All of the aforementioned orthoses are sufficient to provide a patient with a device which is operable to resist plantarflexion. However, it is also the case that each of them has a number of attendant disadvantages.
A first disadvantage is that all of the aforementioned devices are extremely large and bulky bits of equipment which are clearly visible when worn. This means that a patient wearing one of these devices is immediately singled out as being “abnormal”, and this can have a particularly adverse effect on a patient's state of mind.
A further disadvantage is that all of these devices must be worn with shoes, and those shoes may have to have been specially manufactured either to include the appropriate plantarflexion stops (and optional springs), or simply to be large enough in the right places to accommodate an in-shoe medical device. As it is difficult (if not impossible) for a patient to use these devices with normal “off-the-shelf” footwear, the overall cost of the orthosis (including ongoing costs) is typically greatly increased. It also means that a patient who wishes to undertake some activity without shoes, such as swimming for example, would have to undertake that activity without having been provided with any means for resisting plantarflexion.
Another financial disadvantage of these devices is associated with the fact that they each need to be tailored for a particular patient, and fitted by a competent professional. For example, the devices shown in FIGS. 3 to 5 all must be closely moulded by a technician to the shape of the patient's foot and leg, and the fitting process will most likely have to be repeated each time the patient acquires a new pair of shoes.
Another disadvantage associated particularly with the orthoses shown in FIGS. 3 to 5 is that they can be very uncomfortable to wear as the weight of the patient is always bearing down onto a rigid plastics shell. It is not uncommon for the shell to dig into the sole of the patient's foot and cause quite considerable discomfort.
Yet another attendant disadvantage associated particularly with the orthoses shown in FIGS. 3 to 5 is that they typically provide very little dynamic assistance to dorsiflexion of the patient's foot. Typically, the plastics materials used are such that they are relatively difficult to flex and bend, and this means that they are not good at storing energy which can be released to assist dorsiflexion during the swing through phase of a patient's gait cycle.
Another previously proposed orthosis, which avoids some of the aforementioned problems, is described in U.S. Pat. No. 4,559,934. This orthosis is composed of four discrete components, namely an elastic support stocking, a dorsal plate which is anatomically fitted to the dorsum of the foot, an elastic connector which is connected to the bottom end of the plate, and a retaining fitting to which the elastic connector is attached in use. The elastic stocking comprises a standard elastic support stocking such as may be purchased in any pharmacy or chemist, and the plate is attached to the stocking by means of a pair of pockets which are sewn onto the sock. Once the plate has been fitted into the pockets, the elastic connector is drawn through a slit in the plate, and adhered—for example by means of a mechanical hook and loop fastener—to the retaining fitting. By selecting an appropriate tension for the elastic, the foot of the patient can be raised to the required degree.
This device is significantly more inconspicuous and comfortable than the devices shown in FIGS. 1 to 5. However, it still is reasonably noticeable, particularly when the foot is viewed side-on.
It is also the case that it is typically quite difficult for a patient to put the device on and take the device off (due to the number of separate components), and it is very easy for the patient to inadvertently select an insufficient or excessive resistance to plantarflexion simply by pulling too little or too much of the elastic through the slit. This last disadvantage is exacerbated by the fact that it is difficult for the patient to adjust the resistance to plantarflexion when their foot is off the ground, and as a consequence it is not uncommon for a patient wearing such a device to take several attempts to adjust it correctly.
To alleviate the problems set out above, we have previously provided (see granted UK Patent No. 2330309) a sock-like structure which is formed of a resiliently flexible material—such as silicone for example. The sock-like structure, by virtue of its resilience, provides a resistance to plantarflexion and the inherent resilience of the material allows it to store energy which can be released to assist dorsiflexion. The orthosis can be coloured to mimic the colour of the patient's skin (and as such it is cosmetically pleasing), can comfortably be worn in a normal off-the-shelf shoe, and need not be worn with a shoe in order to provide a beneficial effect.
This orthosis provides a quantum leap in the field, and alleviates most of the disadvantages set out above. However, it does still suffer from the disadvantage that it must be carefully fitted by a clinical technician. This means that it can take a considerable amount of time to make and fit the orthosis, and the most immediate drawback of this is that our previously proposed device is still relatively expensive.
It is an aim of the present invention to provide an orthosis which avoids, or at least alleviates, the problems set out above. In particular, it is an aim of the invention to provide an orthosis which functions comparably well to that which we previously proposed, whilst being significantly less expensive to produce.